THE ESCHERICHIA-COLI RECA GENE CAN RESTORE THE DEFECT IN MUTAGENESIS OF THE PSO4-1 MUTANT OF SACCHAROMYCES-CEREVISIAE

The E. coli recA gene was introduced into the pso4-1 mutant of S. cere visiae and transformants were treated with 8-MOP + UVA and 254-nm UV l ight. The results showed that the recA gene increased the resistance t o the toxic effect of 8-MOP + UVA and restored the frequency of revers ion of the pso4-1 mutants after both treatments. The presence of the r ecA gene stimulated expression of the small subunit of the ribonucleot ide reductase (Rnr2) in the pso4-1 mutants. Thus the E. coli recA gene is functional in yeast. Moreover, it was shown that the pso4-1 mutant is epistatic to pso1-1 and rad6-1, which belong to a mutagenic repair pathway. We propose here that the PSO4 gene has some role in the cont rol of mutagenic repair in yeast.